[SOLVED] I'm looking for KECHAO Diyi B1 repair guide or schematics (free) - Phones & Tablets Forum

Hi,

I'm hoping you can help me out with my KECHAO Diyi B1. It's started acting up, and I'm looking for a detailed service manual with boardviews and schematics to properly diagnose and repair it. I need to take precise voltage measurements around the board, so having the right documentation would be very helpful.

Thanks in advance for your help.

Selected Answer

I actually found that service manual on a tech Discord server a while back. A really helpful member there shared a direct link to their blog and I've saved it. I'm happy to pass it along here. Hopefully, these boardviews and schematics help you fix your phone, just like they got me through my repair. Looks like we have the same model.

@Pascal

Absolute legend! That's exactly the info I was searching for. This is going to save me so much time probing in the dark. Seriously, thanks a ton for sharing the link!

Hi there,

I also have the KECHAO Diyi B1 and just downloaded the manual you shared. I'm pretty new to board-level phone repair, and this is a bit intimidating with all the tiny test points and the schematics. Could you point me in the right direction on how to start troubleshooting this ? Any advice on the first few things I should check would be a massive help.

Thanks so much for your time

General advices: start by checking the voltage at the battery connector on the board. With a known-good battery connected, you should see a steady voltage between 3.7V and 4.2V. After that, a great next step is to check the main power management IC (PMIC) for shorts. Using your multimeter in diode mode, check for shorts on the large input capacitors surrounding the PMIC.

Here are a few useful references for troubleshooting your device:
https://www.ifixit.com/Answers/View/589886/dropped+phone+in+the+toilet
Take a look at comment #106
Also, this : https://xdaforums.com/t/new-app-2borange-beta-1.1131078/.
You can also check this video starting from minute 8:

The KECHAO Diyi B1 service manual and boardviews from the link above were exactly what I've been searching for. I couldn't find a complete, free copy anywhere else. Seriously, thank you for sharing this you're a lifesaver!

Hi everyone, I'm working on a KECHAO Diyi B1 with a no power issue and need some guidance with my measurements.
I'm detecting 3.3V on the VREG_MAIN line (pin 1 of the PMIC), which looks good, but I'm getting 0V on the VDD_CPU line (pin 8) where the schematics indicate I should see about 0.9V.
Since this is a core voltage for the application processor, could this missing rail be why the device shows no signs of life?
What's the best procedure to diagnose this further? Should I check for shorts on the CPU rail first, or look at the PMIC's enable signals?
I've already verified the main 3.3V and 1.8V power rails are present and stable.

My KECHAO Diyi B1 was working perfectly until yesterday when it suddenly went completely dead. Now it won't respond to the power button, doesn't vibrate, and shows no signs of life even when connected to a charger. I'm worried there might be a serious issue.

I have a decent multimeter, a basic soldering iron, and a healthy dose of patience. While I've successfully replaced iPhone batteries and charging ports, this will be my first attempt at actual diagnosis. The sheer density of BGA chips and microscopic components is honestly a bit overwhelming.

I'm particularly curious about the alcohol trick I've seen online where you apply isopropyl to the board and look for evaporation hotspots to locate shorts. Is this actually a reliable method for beginners, or are there better approaches I should try first with just a multimeter?

I learned this lesson the hard way last month with mine, it was declared "dead" by two different shops. The phone showed absolutely no signs of life - no charging indicator, no vibration, nothing. Before diving into complex board work, I decided to try one more basic test: wireless charging.

To my complete surprise, it actually heated up on the charging pad! This single discovery completely changed my diagnostic path. It turned out the issue wasn't with the main board or processor, but with the notoriously fragile USB-C port that had failed completely. A $15 replacement part and some careful soldering brought it back to life.

The moral? Always exhaust every external testing method before opening the device. Test wireless charging if available, try different charging methods, and don't assume the worst case scenario. Sometimes the most "dead" devices have the simplest solutions hiding in plain sight.

I suspect my issue might be related to that cheap, third-party fast charger I used at the airport last week... Now the device gets extremely hot during charging, the screen flickers at low brightness, and sometimes it randomly shuts down at 30% battery. Could this have damaged the power management IC or battery calibration?

If your KECHAO Diyi B1 starts acting up, random reboots, fast battery drain, or connectivity issues, there are several diagnostic steps you can take before assuming the worst:

• Check your charging habits: Using poor-quality chargers or wireless pads can gradually damage your battery and charging circuit, leading to unpredictable behavior.
• Inspect the physical components: A slightly damaged charging port, worn battery, or even accumulated pocket lint can cause issues that seem like major hardware failures.
• Monitor temperature patterns: If your phone gets unusually hot during specific tasks (like camera use or gaming), it could point to a failing component rather than a software issue.
• Use diagnostic tools wisely: Ampere for battery health, phone diagnostic codes (*#0*# on many models), and a thermal camera can reveal problems without opening the device.
• Know when to stop: If you see liquid damage indicators tripped or smell burnt electronics, it's time to consult a professional before causing irreversible damage.

Also visit this link it may help : https://xdaforums.com/t/htc-evo-3d-out-now-at-sprint-stores.1125042/

Here's what I discovered on forums and technical databases:

Install reliable third-party battery monitoring apps such as AccuBattery, GSam Battery Monitor, AIDA64, CPU-Z, or Battery Monitor Widget. It manifests as phantom touches on the screen, where the device registers inputs that you aren't making. Addressing these issues can significantly improve your daily smartphone experience, restoring the fluid and responsive operation you expect from your device.A smartphone's ability to connect wirelessly, whether to cellular networks, Wi-Fi, or Bluetooth, is fundamental to its functionality. Manufacturers often release updates that fix bugs, including battery drain issues. For lead-free solder (most modern smartphones), a common starting range is 300-380°C. For stubborn corrosion, you might need to very gently scrape with a plastic spudger or a wooden toothpick, followed by alcohol cleaning. Always use a different, high-quality USB cable known to work perfectly with another device (e.g., the original cable). Before delving into the physical inspection, it's important to understand what antenna contact points are and why they are so critical. The PMIC is the heart of a phone's power distribution system, regulating voltages for nearly every component. Use robust tracking, forecasting, and reorder points to find the sweet spot. After clearing the cache, restart your phone and test the navigation bar. You simply access your secure folder as usual using your established PIN, pattern, or biometric authentication. Compare the bent pins to the adjacent, correctly aligned pins to gauge the proper orientation and height. Just as a chef needs their knives and a carpenter their saw, a smartphone repair technician relies on a specific set of precision instruments. Examine the small connector at the end of the flex cable for bent pins, debris, or a poor fit into the logic board connector. The cold plate method (often involving a specialized freezer separation machine or simply placing the phone in a very cold environment, like a deep freezer with specific preparations) aims to achieve the opposite effect. Remove Back Cover/Screen: Once all cables are disconnected, set the back cover/screen safely aside. Hot Air Rework Station: Essential for desoldering and re-soldering soldered shields. Sometimes, factory resetting the phone or updating the software can help calibrate new sensors. Such an issue can range from a minor annoyance to a precursor of significant functional problems or even a safety hazard. If the problem persists and you suspect deep-seated software corruption, a factory reset might be necessary. Reconnect its flex cable to the logic board, ensuring it clicks securely. Physical Damage: Bent pins on the display connector, cracked components (small black ICs, capacitors, resistors), signs of burning. If not, apply a very thin, even bead of B-7000 or T-7000 adhesive to the mounting surface on the phone or to the back of the new ring itself. PC with USB Drivers: Install the correct USB drivers for your phone's manufacturer on your computer. Gently pull up on the suction cup while simultaneously inserting a thin prying tool (like a guitar pick or plastic card) into the gap created between the glass and the phone frame. They vary widely in size, from barely visible 01005 (0.4mm x 0.2mm) to larger 0402 or 0603 packages. Schematics & Boardview Software: Absolutely indispensable for identifying specific OCP/OVP ICs, charging pathways, test points, and component values. Use a nozzle appropriate for the size of the connector, directing the hot air evenly over the connector. If it fails with an error code (e.g., Error 9, 4013, 4014), it often points to hardware issues (e.g., NAND storage, flex cables, or other logic board components).

@Pepe, Not sure what you're trying to say but ok :)